1. Field of the Invention
The present invention relates to a coarse particle separator for separating and collecting coarse particles and, more particularly, to a coarse particle separator for separating and collecting coarse particles having a size greater than approximately 500 microns.
2. Description of the Related Art
Image formation processes commonly use toner particles in the development stage of the image formation. To obtain a quality image, the toner particles used in the development stage must fall within an acceptable range of particle sizes.
When providing toner particles within a prescribed particle size range, unacceptable particles must be separated out to yield toner particles having an appropriate particle size. Such unacceptable particles include coarse particles which often have a mass as great as 125,000 times as great as the mass of an acceptable toner particle.
In conveying the toner particles for packaging, an effective system for separating out coarse particles is required.
U.S. Pat. No. 4,304,360 to Luhr et al. discloses a process for the manufacture of xerographic toner and for particle classification using a cyclone separator whose exit duct length is controlled to achieve lower particle size classification by causing particles below a five micron diameter to exit the separator through an upper exit duct. The finished product exits through a lower output port. The reference further discloses a coarse classifier. The coarse classifier's incoming material is directed upward toward the bottom of a cone-shaped rotor having radial fins. Larger particles are accelerated to the classifier's annular wall. Finer particles migrate through the rotors fins with a rising air stream and pass out of the classifier by way of an exit duct. The large particles fall down through a chamber. A rotary valve is continuously operated to supply the particles for further grinding. Secondary air is further supplied to the classifier by way of a blower. The device requires that rotor speed be monitored and controlled in order to obtain acceptable toner particles.
U.S. Pat. No. 4,802,977 to Kanda et al. discloses a process for classifying toner particles for developing electrostatic images with accurate particle size distribution. A reduced pressure is generated in a classifying chamber which is divided into at least three sections including a coarse powder section having a first outlet for withdrawing coarse particles, a second outlet for withdrawing medium particles and a third outlet for withdrawing fine powder. A reduced pressure is applied to the chamber through at least one of the first to third outlets.
U.S. Pat. No. 4,132,634 to Rumpf et al. discloses a method and apparatus for sifting particulate material in a cross current where all of the particles of the same size are propelled transversely at the same velocity with the same direction.
U.S. Pat. No. 4,551,240 to Beppu et al. discloses an apparatus for classifying various kinds of particles of different sizes with air currents. The particles are provided with forces of inertia differing from one another depending upon size. The flow of air current constitutes a flow adjusting air current layer interposed between walls defining the main and subsidiary passages and the particular material conveyed by the air currents.
A coarse particle separator is desired which has the ability to separate unacceptable toner particles, thereby improving the product quality, yield and packaging throughout as toner particles are being processed and packaged.